While Android’s developer platform is getting some intense competition from Apple, Google said today that more than 250,000 apps have been downloaded a total of more than 6 billion times to date — that’s double the three billion it reported last quarter. The first billion downloads took 20 months, and the second billion took five months, so the trend is the up-and-to-the-right hockey stick of growth that Android needs to continue attracting developers.

Overall, the 400 types of devices running the operating system now add up to 135 million activations worldwide, around what we’d guessed after the company said it had hit 100 million in May. New activations per day are up from 500,000 only a couple of weeks ago to 550,000 now.

“Despite the efforts of some of our competitors, there hasn’t been any slow down. Partners and developers are continuing to expand the ecosystem,” chief executive Larry Page said on the call, referring variously to Android’s ongoing patent issues and competitors like Apple. He also noted that there are 231 carriers in 123 countries offering Android devices, with 78 industry partners now in the Android alliance.